Systems and methods for optimizing ssl handshake processing

ABSTRACT

A method for buffering SSL handshake messages prior to computing a message digest for the SSL handshake includes: conducting, by an appliance with a client, an SSL handshake, the SSL handshake comprising a plurality of SSL handshake messages; storing, by the appliance, the plurality of SSL handshake messages; providing, by the appliance to a message digest computing device in response to receiving a client finish message corresponding to the SSL handshake, the plurality of SSL handshake messages; receiving, by the appliance from the message digest computing device, a message digest corresponding to the provided messages; determining by the appliance, the message digest matches a message digest included in the SSL client finish message; and completing, by the appliance with the client, the SSL handshake. Corresponding systems are also described.

FIELD OF THE INVENTION

The present invention relates to computer networking technologies, andmore specifically, to systems and methods for improving the efficiencyof secure communication initialization.

BACKGROUND OF THE INVENTION

Many networking applications require secure and authenticatedcommunications. SSL and its related protocols are often used to enablesecure communications between a client and a server. One drawback of SSLis that the handshake required to initiate an SSL connection may requiresignificant computing resources, slowing down client access. Onesolution to this problem is to offload the task of SSL processing to anetwork appliance, which may sit in front of a server on a network andhandle SSL connection requests. The appliance may then transmit datareceived via the SSL communications to the server either via a nonsecurechannel or via a single SSL connection using connection poolingtechniques.

However, this solution may not be adequate for all networks. ComputingSSL handshake messages may be a processor intensive task, and thusreduce the number of appliance processor cycles available for othertasks, such as servicing existing connections, load balancing, andcaching. Thus there exists a need for systems and methods whichaccelerate the generation and processing of SSL handshake messages on anetwork appliance.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a method for bufferingSSL handshake messages prior to computing a message digest for the SSLhandshake, the method comprising: conducting, by an appliance with aclient, an SSL handshake, the SSL handshake comprising a plurality ofSSL handshake messages; storing, by the appliance, the plurality of SSLhandshake messages; providing, by the appliance to a message digestcomputing device in response to receiving a client finish messagecorresponding to the SSL handshake, the plurality of SSL handshakemessages; receiving, by the appliance from the message digest computingdevice, a message digest corresponding to the provided messages;determining by the appliance, the message digest matches a messagedigest included in the SSL client finish message; and completing, by theappliance with the client, the SSL handshake.

In a second aspect, the present invention relates to a computerimplemented system for buffering SSL handshake messages prior tocomputing a message digest for the SSL handshake, the system comprising:a network appliance which conducts, with a client, an SSL handshake, theSSL handshake comprising a plurality of SSL handshake messages; storing,by the appliance, the plurality of SSL handshake messages; providing, toa message digest computing device in response to receiving a clientfinish message corresponding to the SSL handshake, the plurality of SSLhandshake messages; receiving, from the message digest computing device,a message digest corresponding to the provided messages; determining,the message digest matches a message digest included in the SSL clientfinish message; and completing, with the client, the SSL handshake; anda message digest computing device which computes a message digestcorresponding to one or more received messages.

In a third aspect, the present invention relates to a method forenabling efficient SSL handshakes through precomputing of handshakemessages, the method comprising: receiving, by an appliance, a servercertificate identifying a server; generating, by the appliance, at leastone of: (i) an SSL server certificate message comprising the receivedserver certificate, (ii) an SSL client certificate request message, and(iii) an SSL hello done message; storing, by the appliance, thegenerated messages; receiving, by the appliance from a client, an SSLclient hello message identifying the server; and transmitting, by theappliance to the client, an SSL server hello message and at least one ofthe stored messages.

In a fourth aspect, the present invention relates to a computerimplemented system for enabling efficient SSL handshakes throughprecomputing of handshake messages, the system comprising: a networkappliance which receives a server certificate identifying a server;generates at least one of: (i) an SSL server certificate messagecomprising the received server certificate, (ii) an SSL clientcertificate request message, and (iii) an SSL hello done message; storesthe generated messages; receives, from a client, an SSL client hellomessage identifying the server; and transmits, to the client, an SSLserver hello message and at least one of the stored messages.

In a fifth aspect, the present invention relates to a method for using anetwork appliance to efficiently buffer and encrypt data fortransmission, the method comprising: receiving, by an appliance via aconnection, a first SSL record, the first record comprising a firstencrypted message; decrypting, by the appliance, the first encryptedmessage to produce a first decrypted message; buffering, by theappliance, the first decrypted message; receiving, by the appliance viathe connection, a second SSL record, the second record comprising asecond encrypted message; decrypting, by the appliance, the secondencrypted message to produce a second decrypted message; determining, bythe appliance, that a transmittal condition has been satisfied;encrypting, by the appliance in response to the determination, the firstdecrypted message and a portion of the second decrypted message toproduce a third SSL record; and transmitting, by the appliance via asecond connection, the third record.

In a sixth aspect the present invention relates to a computerimplemented system for efficiently buffering and encrypting data fortransmission, the system comprising: a network appliance which receives,via a connection, a first SSL record, the first record comprising afirst encrypted message; decrypts the first encrypted message to producea first decrypted message; buffers the first decrypted message;receives, via the connection, a second SSL record, the second recordcomprising a second encrypted message; decrypts the second encryptedmessage to produce a second decrypted message; determines that atransmittal condition has been satisfied; encrypts, in response to thedetermination, the first decrypted message and a portion of the seconddecrypted message to produce a third SSL record; and transmits, via asecond connection, the third record.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via an appliance;

FIG. 1B is a block diagram of an embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIGS. 1C and 1D are block diagrams of embodiments of a computing device;

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server;

FIG. 2B is a block diagram of another embodiment of an appliance foroptimizing, accelerating, load-balancing and routing communicationsbetween a client and a server;

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server via the appliance;

FIG. 4A is a flow diagram of an example SSL handshake;

FIG. 4B is, a flow diagram of an appliance utilizing bulk decryption;

FIG. 4C is a flow diagram of an appliance providing bulk encryption;

FIG. 5 is a flow diagram of a method for buffering SSL handshakemessages prior to computing a message digest for the SSL handshake;

FIG. 6 is a method for enabling efficient SSL handshakes throughprecomputing of handshake messages; and

FIG. 7 is a flow diagram of a method for using a network appliance toefficiently buffer and encrypt data for transmission

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION OF THE INVENTION A. Network and ComputingEnvironment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environmentcomprises one or more clients 102 a-102 n (also generally referred to aslocal machine(s) 102, or client(s) 102) in communication with one ormore servers 106 a-106 n (also generally referred to as server(s) 106,or remote machine(s) 106) via one or more networks 104, 104′ (generallyreferred to as network 104). In some embodiments, a client 102communicates with a server 106 via an appliance 200.

Although FIG. 1A shows a network 104 and a network 104′ between theclients 102 and the servers 106, the clients 102 and the servers 106 maybe on the same network 104. The networks 104 and 104′ can be the sametype of network or different types of networks. The network 104 and/orthe network 104′ can be a local-area network (LAN), such as a companyIntranet, a metropolitan area network (MAN), or a wide area network(WAN), such as the Internet or the World Wide Web. In one embodiment,network 104′ may be a private network and network 104 may be a publicnetwork. In some embodiments, network 104 may be a private network andnetwork 104′ a public network. In another embodiment, networks 104 and104′ may both be private networks. In some embodiments, clients 102 maybe located at a branch office of a corporate enterprise communicatingvia a WAN connection over the network 104 to the servers 106 located ata corporate data center.

The network 104 and/or 104′ be any type and/or form of network and mayinclude any of the following: a point to point network, a broadcastnetwork, a wide area network, a local area network, a telecommunicationsnetwork, a data communication network, a computer network, an ATM(Asynchronous Transfer Mode) network, a SONET (Synchronous OpticalNetwork) network, a SDH (Synchronous Digital Hierarchy) network, awireless network and a wireline network. In some embodiments, thenetwork 104 may comprise a wireless link, such as an infrared channel orsatellite band. The topology of the network 104 and/or 104′ may be abus, star, or ring network topology. The network 104 and/or 104′ andnetwork topology may be of any such network or network topology as knownto those ordinarily skilled in the art capable of supporting theoperations described herein.

As shown in FIG. 1A, the appliance 200, which also may be referred to asan interface unit 200 or gateway 200, is shown between the networks 104and 104′. In some embodiments, the appliance 200 may be located onnetwork 104. For example, a branch office of a corporate enterprise maydeploy an appliance 200 at the branch office. In other embodiments, theappliance 200 may be located on network 104′. For example, an appliance200 may be located at a corporate data center. In yet anotherembodiment, a plurality of appliances 200 may be deployed on network104. In some embodiments, a plurality of appliances 200 may be deployedon network 104′. In one embodiment, a first appliance 200 communicateswith a second appliance 200′. In other embodiments, the appliance 200could be a part of any client 102 or server 106 on the same or differentnetwork 104,104′ as the client 102. One or more appliances 200 may belocated at any point in the network or network communications pathbetween a client 102 and a server 106.

In one embodiment, the system may include multiple, logically-groupedservers 106. In these embodiments, the logical group of servers may bereferred to as a server farm 38. In some of these embodiments, theserves 106 may be geographically dispersed. In some cases, a farm 38 maybe administered as a single entity. In other embodiments, the serverfarm 38 comprises a plurality of server farms 38. In one embodiment, theserver farm executes one or more applications on behalf of one or moreclients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or medium-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The clients 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality required to identify and provide address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Referring now to FIG. 1B, a network environment for delivering and/oroperating a computing environment on a client 102 is depicted. In someembodiments, a server 106 includes an application delivery system 190for delivering a computing environment or an application and/or datafile to one or more clients 102. In brief overview, a client 10 is incommunication with a server 106 via network 104, 104′ and appliance 200.For example, the client 102 may reside in a remote office of a company,e.g., a branch office, and the server 106 may reside at a corporate datacenter. The client 102 comprises a client agent 120, and a computingenvironment 15. The computing environment 15 may execute or operate anapplication that accesses, processes or uses a data file. The computingenvironment 15, application and/or data file may be delivered via theappliance 200 and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 15, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 15 by the application delivery system 190. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file processable by theapplication from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. The appliance 200 may provide accelerationtechniques for accelerating any transport layer payload from a server106 to a client 102, such as: 1) transport layer connection pooling, 2)transport layer connection multiplexing, 3) transport control protocolbuffering, 4) compression and 5) caching. In some embodiments, theappliance 200 provides load balancing of servers 106 in responding torequests from clients 102. In other embodiments, the appliance 200 actsas a proxy or access server to provide access to the one or more servers106. In another embodiment, the appliance 200 provides a secure virtualprivate network connection from a first network 104 of the client 102 tothe second network 104′ of the server 106, such as an SSL VPNconnection. It yet other embodiments, the appliance 200 providesapplication firewall security, control and management of the connectionand communications between a client 102 and a server 106.

In some embodiments, the application delivery management system 190provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 195. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 190 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 190 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 190 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 190 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 190, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 190, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 190 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 15 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 190 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 15 on client 102.

In some embodiments, the application delivery system 190 comprises anyportion of the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™ and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application delivery system 190 may deliver one ormore applications to clients 102 or users via a remote-display protocolor otherwise via remote-based or server-based computing. In anotherembodiment, the application delivery system 190 may deliver one or moreapplications to clients or users via steaming of the application.

In one embodiment, the application delivery system 190 includes a policyengine 195 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 195 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 195 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 190 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 190 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 190 enumerates a plurality of application programsavailable to the client 102. The application delivery system 190receives a request to execute an enumerated application. The applicationdelivery system 190 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 190 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 190may select a method of execution of the application enabling the localmachine 10 to execute the application program locally after retrieving aplurality of application files comprising the application. In yetanother embodiment, the application delivery system 190 may select amethod of execution of the application to stream the application via thenetwork 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiments the server 106 may display output to the client 102 usingany thin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™, and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application is an ICA client, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla. In other embodiments, theapplication includes a Remote Desktop (RDP) client, developed byMicrosoft Corporation of Redmond, Wash. Also, the server 106 may run anapplication, which for example, may be an application server providingemail services such as Microsoft Exchange manufactured by the MicrosoftCorporation of Redmond, Wash., a web or Internet server, or a desktopsharing server, or a collaboration server. In some embodiments, any ofthe applications may comprise any type of hosted service or products,such as GoToMeeting™ provided by Citrix Online Division, Inc. of SantaBarbara, Calif., WebEx™ provided by WebEx, Inc. of Santa Clara, Calif.,or Microsoft Office Live Meeting provided by Microsoft Corporation ofRedmond, Wash.

The client 102, server 106, and appliance 200 may be deployed as and/orexecuted on any type and form of computing device, such as a computer,network device or appliance capable of communicating on any type andform of network and performing the operations described herein. FIGS. 1Cand 1D depict block diagrams of a computing device 100 useful forpracticing an embodiment of the client 102, server 106 or appliance 200.As shown in FIGS. 1C and 1D, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1C, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC 100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1C, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1C depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1D the main memory 122 maybe DRDRAM.

FIG. 1D depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1C, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1D depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130via HyperTransport, Rapid I/O, or InfiniBand. FIG. 1D also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 using a localinterconnect bus while communicating with I/O device 130 directly.

The computing device 100 may support any suitable installation device116, such as a floppy disk drive for receiving floppy disks such as3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive,a DVD-ROM drive, tape drives of various formats, USB device, hard-driveor any other device suitable for installing software and programs suchas any client agent 120, or portion thereof. The computing device 100may further comprise a storage device 128, such as one or more hard diskdrives or redundant arrays of independent disks, for storing anoperating system and other related software, and for storing applicationsoftware programs such as any program related to the client agent 120.Optionally, any of the installation devices 116 could also be used asthe storage device 128. Additionally, the operating system and thesoftware can be run from a bootable medium, for example, a bootable CD,such as KNOPPIX®, a bootable CD for GNU/Linux that is available as aGNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein.

A wide variety of I/O devices 130 a-130 n may be present in thecomputing device 100. Input devices include keyboards, mice, trackpads,trackballs, microphones, and drawing tablets. Output devices includevideo displays, speakers, inkjet printers, laser printers, anddye-sublimation printers. The I/O devices 130 may be controlled by anI/O controller 123 as shown in FIG. 1C. The I/O controller may controlone or more I/O devices such as a keyboard 126 and a pointing device127, e.g., a mouse or optical pen. Furthermore, an I/O device may alsoprovide storage 128 and/or an installation medium 116 for the computingdevice 100. In still other embodiments, the computing device 100 mayprovide USB connections to receive handheld USB storage devices such asthe USB Flash Drive line of devices manufactured by Twintech Industry,Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, an I/O device 130 may be a bridge 170 betweenthe system bus 150 and an external communication bus, such as a USB bus,an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, aFireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, aGigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, aSuper HIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus,or a Serial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1C and 1D typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, Calif.; OS/2, manufacturedby International Business Machines of Armonk, N.Y.; and Linux, afreely-available operating system distributed by Caldera Corp. of SaltLake City, Utah, or any type and/or form of a Unix operating system,among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

B. Appliance Architecture

FIG. 2A illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting. As shown in FIG.2, appliance 200 comprises a hardware layer 206 and a software layerdivided into a user space 202 and a kernel space 204.

Hardware layer 206 provides the hardware elements upon which programsand services within kernel space 204 and user space 202 are executed.Hardware layer 206 also provides the structures and elements which allowprograms and services within kernel space 204 and user space 202 tocommunicate data both internally and externally with respect toappliance 200. As shown in FIG. 2, the hardware layer 206 includes aprocessing unit 262 for executing software programs and services, amemory 264 for storing software and data, network ports 266 fortransmitting and receiving data over a network, and an encryptionprocessor 260 for performing functions related to Secure Sockets Layerprocessing of data transmitted and received over the network. In someembodiments, the central processing unit 262 may perform the functionsof the encryption processor 260 in a single processor. Additionally, thehardware layer 206 may comprise multiple processors for each of theprocessing unit 262 and the encryption processor 260. The processor 262may include any of the processors 101 described above in connection withFIGS. 1C and 1D. In some embodiments, the central processing unit 262may perform the functions of the encryption processor 260 in a singleprocessor. Additionally, the hardware layer 206 may comprise multipleprocessors for each of the processing unit 262 and the encryptionprocessor 260. For example, in one embodiment, the appliance 200comprises a first processor 262 and a second processor 262′. In otherembodiments, the processor 262 or 262′ comprises a multi-core processor.

Although the hardware layer 206 of appliance 200 is generallyillustrated with an encryption processor 260, processor 260 may be aprocessor for performing functions related to any encryption protocol,such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)protocol. In some embodiments, the processor 260 may be a generalpurpose processor (GPP), and in further embodiments, may be haveexecutable instructions for performing processing of any securityrelated protocol.

Although the hardware layer 206 of appliance 200 is illustrated withcertain elements in FIG. 2, the hardware portions or components ofappliance 200 may comprise any type and form of elements, hardware orsoftware, of a computing device, such as the computing device 100illustrated and discussed herein in conjunction with FIGS. 1C and 1D. Insome embodiments, the appliance 200 may comprise a server, gateway,router, switch, bridge or other type of computing or network device, andhave any hardware and/or software elements associated therewith.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into kernel space 204 and userspace 204. In example software architecture 200, the operating systemmay be any type and/or form of Unix operating system although theinvention is not so limited. As such, the appliance 200 can be runningany operating system such as any of the versions of the Microsoft®Windows operating systems, the different releases of the Unix and Linuxoperating systems, any version of the Mac OS® for Macintosh computers,any embedded operating system, any network operating system, anyreal-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices or network devices, or any other operating system capable ofrunning on the appliance 200 and performing the operations describedherein.

The kernel space 204 is reserved for running the kernel 230, includingany device drivers, kernel extensions or other kernel related software.As known to those skilled in the art, the kernel 230 is the core of theoperating system, and provides access, control, and management ofresources and hardware-related elements of the application 104. Inaccordance with an embodiment of the appliance 200, the kernel space 204also includes a number of network services or processes working inconjunction with a cache manager 232. sometimes also referred to as theintegrated cache, the benefits of which are described in detail furtherherein. Additionally, the embodiment of the kernel 230 will depend onthe embodiment of the operating system installed, configured, orotherwise used by the device 200.

In one embodiment, the device 200 comprises one network stack 267, suchas a TCP/IP based stack, for communicating with the client 102 and/orthe server 106. In one embodiment, the network stack 267 is used tocommunicate with a first network, such as network 108, and a secondnetwork 110. In some embodiments, the device 200 terminates a firsttransport layer connection, such as a TCP connection of a client 102,and establishes a second transport layer connection to a server 106 foruse by the client 102, e.g., the second transport layer connection isterminated at the appliance 200 and the server 106. The first and secondtransport layer connections may be established via a single networkstack 267. In other embodiments, the device 200 may comprise multiplenetwork stacks, for example 267 and 267′, and the first transport layerconnection may be established or terminated at one network stack 267,and the second transport layer connection on the second network stack267′. For example, one network stack may be for receiving andtransmitting network packet on a first network, and another networkstack for receiving and transmitting network packets on a secondnetwork. In one embodiment, the network stack 267 comprises a buffer 243for queuing one or more network packets for transmission by theappliance 200.

As shown in FIG. 2, the kernel space 204 includes the cache manager 232,a high-speed layer 2-7 integrated packet engine 240, an encryptionengine 234, a policy engine 236 and multi-protocol compression logic238. Running these components or processes 232, 240, 234, 236 and 238 inkernel space 204 or kernel mode instead of the user space 202 improvesthe performance of each of these components, alone and in combination.Kernel operation means that these components or processes 232, 240, 234,236 and 238 run in the core address space of the operating system of thedevice 200. For example, running the encryption engine 234 in kernelmode improves encryption performance by moving encryption and decryptionoperations to the kernel, thereby reducing the number of transitionsbetween the memory space or a kernel thread in kernel mode and thememory space or a thread in user mode. For example, data obtained inkernel mode may not need to be passed or copied to a process or threadrunning in user mode, such as from a kernel level data structure to auser level data structure. In another aspect, the number of contextswitches between kernel mode and user mode are also reduced.Additionally, synchronization of and communications between any of thecomponents or processes 232, 240, 235, 236 and 238 can be performed moreefficiently in the kernel space 204.

In some embodiments, any portion of the components 232, 240, 234, 236and 238 may run or operate in the kernel space 204, while other portionsof these components 232, 240, 234, 236 and 238 may run or operate inuser space 202. In one embodiment, the appliance 200 uses a kernel-leveldata structure providing access to any portion of one or more networkpackets, for example, a network packet comprising a request from aclient 102 or a response from a server 106. In some embodiments, thekernel-level data structure may be obtained by the packet engine 240 viaa transport layer driver interface or filter to the network stack 267.The kernel-level data structure may comprise any interface and/or dataaccessible via the kernel space 204 related to the network stack 267,network traffic or packets received or transmitted by the network stack267. In other embodiments, the kernel-level data structure may be usedby any of the components or processes 232, 240, 234, 236 and 238 toperform the desired operation of the component or process. In oneembodiment, a component 232, 240, 234, 236 and 238 is running in kernelmode 204 when using the kernel-level data structure, while in anotherembodiment, the component 232, 240, 234, 236 and 238 is running in usermode when using the kernel-level data structure. In some embodiments,the kernel-level data structure may be copied or passed to a secondkernel-level data structure, or any desired user-level data structure.

The cache manager 232 may comprise software, hardware or any combinationof software and hardware to provide cache access, control and managementof any type and form of content, such as objects or dynamicallygenerated objects served by the originating servers 106. The data,objects or content processed and stored by the cache manager 232 maycomprise data in any format, such as a markup language, or communicatedvia any protocol. In some embodiments, the cache manager 232 duplicatesoriginal data stored elsewhere or data previously computed, generated ortransmitted, in which the original data may require longer access timeto fetch, compute or otherwise obtain relative to reading a cache memoryelement. Once the data is stored in the cache memory element, future usecan be made by accessing the cached copy rather than refetching orrecomputing the original data, thereby reducing the access time. In someembodiments, the cache memory element nat comprise a data object inmemory 264 of device 200. In other embodiments, the cache memory elementmay comprise memory having a faster access time than memory 264. Inanother embodiment, the cache memory element may comrpise any type andform of storage element of the device 200, such as a portion of a harddisk. In some embodiments, the processing unit 262 may provide cachememory for use by the cache manager 232. In yet further embodiments, thecache manager 232 may use any portion and combination of memory,storage, or the processing unit for caching data, objects, and othercontent.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any embodiments of the techniques of theappliance 200 described herein. For example, the cache manager 232includes logic or functionality to invalidate objects based on theexpiration of an invalidation time period or upon receipt of aninvalidation command from a client 102 or server 106. In someembodiments, the cache manager 232 may operate as a program, service,process or task executing in the kernel space 204, and in otherembodiments, in the user space 202. In one embodiment, a first portionof the cache manager 232 executes in the user space 202 while a secondportion executes in the kernel space 204. In some embodiments, the cachemanager 232 can comprise any type of general purpose processor (GPP), orany other type of integrated circuit, such as a Field Programmable GateArray (FPGA), Programmable Logic Device (PLD), or Application SpecificIntegrated Circuit (ASIC).

The policy engine 236 may include, for example, an intelligentstatistical engine or other programmable application(s). In oneembodiment, the policy engine 236 provides a configuration mechanism toallow a user to identifying, specify, define or configure a cachingpolicy. Policy engine 236, in some embodiments, also has access tomemory to support data structures such as lookup tables or hash tablesto enable user-selected caching policy decisions. In other embodiments,the policy engine 236 may comprise any logic, rules, functions oroperations to determine and provide access, control and management ofobjects, data or content being cached by the appliance 200 in additionto access, control and management of security, network traffic, networkaccess, compression or any other function or operation performed by theappliance 200. Further examples of specific caching policies are furtherdescribed herein.

The encryption engine 234 comprises any logic, business rules, functionsor operations for handling the processing of any security relatedprotocol, such as SSL or TLS, or any function related thereto. Forexample, the encryption engine 234 encrypts and decrypts networkpackets, or any portion thereof, communicated via the appliance 200. Theencryption engine 234 may also setup or establish SSL or TLS connectionson behalf of the client 102 a-102 n, server 106 a-106 n, or appliance200. As such, the encryption engine 234 provides offloading andacceleration of SSL processing. In one embodiment, the encryption engine234 uses a tunneling protocol to provide a virtual private networkbetween a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine 234 is in communication with theEncryption processor 260. In other embodiments, the encryption engine234 comprises executable instructions running on the Encryptionprocessor 260.

The multi-protocol compression engine 238 comprises any logic, businessrules, function or operations for compressing one or more protocols of anetwork packet, such as any of the protocols used by the network stack267 of the device 200. In one embodiment, multi-protocol compressionengine 238 compresses bi-directionally between clients 102 a-102 n andservers 106 a-106 n any TCP/IP based protocol, including MessagingApplication Programming Interface (MAPI) (email), File Transfer Protocol(FTP), HyperText Transfer Protocol (HTTP), Common Internet File System(CIFS) protocol (file transfer), Independent Computing Architecture(ICA) protocol, Remote Desktop Protocol (RDP), Wireless ApplicationProtocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP) protocol.In other embodiments, multi-protocol compression engine 238 providescompression of Hypertext Markup Language (HTML) based protocols and insome embodiments, provides compression of any markup languages, such asthe Extensible Markup Language (XML). In one embodiment, themulti-protocol compression engine 238 provides compression of anyhigh-performance protocol, such as any protocol designed for appliance200 to appliance 200 communications. In another embodiment, themulti-protocol compression engine 238 compresses any payload of or anycommunication using a modified transport control protocol, such asTransaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),TCP with large windows (TCP-LW), a congestion prediction protocol suchas the TCP-Vegas protocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine 238 by executing in the kernel mode204 and integrating with packet processing engine 240 accessing thenetwork stack 267 is able to compress any of the protocols carried bythe TCP/IP protocol, such as any application layer protocol.

High speed layer 2-7 integrated packet engine 240, also generallyreferred to as a packet processing engine or packet engine, isresponsible for managing the kernel-level processing of packets receivedand transmitted by appliance 200 via network ports 266. The high speedlayer 2-7 integrated packet engine 240 may comprise a buffer for queuingone or more network packets during processing, such as for receipt of anetwork packet or transmission of a network packer. Additionally, thehigh speed layer 2-7 integrated packet engine 240 is in communicationwith one or more network stacks 267 to send and receive network packetsvia network ports 266. The high speed layer 2-7 integrated packet engine240 works in conjunction with encryption engine 234, cache manager 232,policy engine 236 and multi-protocol compression logic 238. Inparticular, encryption engine 234 is configured to perform SSLprocessing of packets, policy engine 236 is configured to performfunctions related to traffic management such as request-level contentswitching and request-level cache redirection, and multi-protocolcompression logic 238 is configured to perform functions related tocompression and decompression of data.

The high speed layer 2-7 integrated packet engine 240 includes a packetprocessing timer 242. In one embodiment, the packet processing timer 242provides one or more time intervals to trigger the processing ofincoming, i.e., received, or outgoing, i.e., transmitted, networkpackets. In some embodiments, the high speed layer 2-7 integrated packetengine 240 processes network packets responsive to the timer 242. Thepacket processing timer 242 provides any type and form of signal to thepacket engine 240 to notify, trigger, or communicate a time relatedevent, interval or occurrence. In many embodiments, the packetprocessing timer 242 operates in the order of milliseconds, such as forexample 100 ms, 50 ms or 25 ms. For example, in some embodiments, thepacket processing timer 242 provides time intervals or otherwise causesa network packet to be processed by the high speed layer 2-7 integratedpacket engine 240 at a 10 ms time interval, while in other embodiments,at a 5 ms time interval, and still yet in further embodiments, as shortas a 3, 2, or 1 ms time interval. The high speed layer 2-7 integratedpacket engine 240 may be interfaced, integrated or in communication withthe encryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression engine 238 during operation. As such, any ofthe logic, functions, or operations of the encryption engine 234, cachemanager 232, policy engine 236 and multi-protocol compression logic 238may be performed responsive to the packet processing timer 242 and/orthe packet engine 240. Therefore, any of the logic, functions, oroperations of the encryption engine 234, cache manager 232, policyengine 236 and multi-protocol compression logic 238 may be performed atthe granularity of time intervals provided via the packet processingtimer 242, for example, at a time interval of less than or equal to 10ms. For example, in one embodiment, the cache manager 232 may performinvalidation of any cached objects responsive to the high speed layer2-7 integrated packet engine 240 and/or the packet processing timer 242.In another embodiment, the expiry or invalidation time of a cachedobject can be set to the same order of granularity as the time intervalof the packet processing timer 242, such as at every 10 ms

In contrast to kernel space 204, user space 202 is the memory area orportion of the operating system used by user mode applications orprograms otherwise running in user mode. A user mode application may notaccess kernel space 204 directly and uses service calls in order toaccess kernel services. As shown in FIG. 2, user space 202 of appliance200 includes a graphical user interface (GUI) 210, a command lineinterface (CLI) 212, shell services 214, health monitoring program 216,and daemon services 218. GUI 210 and CLI 212 provide a means by which asystem administrator or other user can interact with and control theoperation of appliance 200, such as via the operating system of theappliance 200 and either is user space 202 or kernel space 204. The GUI210 may be any type and form of graphical user interface and may bepresented via text, graphical or otherwise, by any type of program orapplication, such as a browser. The CLI 212 may be any type and form ofcommand line or text-based interface, such as a command line provided bythe operating system. For example, the CLI 212 may comprise a shell,which is a tool to enable users to interact with the operating system.In some embodiments, the CLI 212 may be provided via a bash, csh, tcsh,or ksh type shell. The shell services 214 comprises the programs,services, tasks, processes or executable instructions to supportinteraction with the appliance 200 or operating system by a user via theGUI 210 and/or CLI 212.

Health monitoring program 216 is used to monitor, check, report andensure that network systems are functioning properly and that users arereceiving requested content over a network. Health monitoring program216 comprises one or more programs, services, tasks, processes orexecutable instructions to provide logic, rules, functions or operationsfor monitoring any activity of the appliance 200. In some embodiments,the health monitoring program 216 intercepts and inspects any networktraffic passed via the appliance 200. In other embodiments, the healthmonitoring program 216 interfaces by any suitable means and/ormechanisms with one or more of the following: the encryption engine 234,cache manager 232, policy engine 236, multi-protocol compression logic238, packet engine 240, daemon services 218, and shell services 214. Assuch, the health monitoring program 216 may call any applicationprogramming interface (API) to determine a state, status, or health ofany portion of the appliance 200. For example, the health monitoringprogram 216 may ping or send a status inquiry on a periodic basis tocheck if a program, process, service or task is active and currentlyrunning. In another example, the health monitoring program 216 may checkany status, error or history logs provided by any program, process,service or task to determine any condition, status or error with anyportion of the appliance 200.

Daemon services 218 are programs that run continuously or in thebackground and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests toother programs or processes, such as another daemon service 218 asappropriate. As known to those skilled in the art, a daemon service 218may run unattended to perform continuous or periodic system widefunctions, such as network control, or to perform any desired task. Insome embodiments, one or more daemon services 218 run in the user space202, while in other embodiments, one or more daemon services 218 run inthe kernel space.

Referring now to FIG. 2B, another embodiment of the appliance 200 isdepicted. In brief overview, the appliance 200 provides one or more ofthe following services, functionality or operations: SSL VPNconnectivity 280, switching/load balancing 284, Domain Name Serviceresolution 286, acceleration 288 and an application firewall 290 forcommunications between one or more clients 102 and one or more servers106. In one embodiment, the appliance 200 comprises any of the networkdevices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,referred to as Citrix NetScaler devices. Each of the servers 106 mayprovide one or more network related services 270 a-270 n (referred to asservices 270). For example, a server 106 may provide an http service270. The appliance 200 comprises one or more virtual servers or virtualinternet protocol servers, referred to as a vServer, VIP server, or justVIP 275 a-275 n (also referred herein as vServer 275). The vServer 275receives, intercepts or otherwise processes communications between aclient 102 and a server 106 in accordance with the configuration andoperations of the appliance 200.

The vServer 275 may comprise software, hardware or any combination ofsoftware and hardware. The vServer 275 may comprise any type and form ofprogram, service, task, process or executable instructions operating inuser mode 202, kernel mode 204 or any combination thereof in theappliance 200. The vServer 275 includes any logic, functions, rules, oroperations to perform any embodiments of the techniques describedherein, such as SSL VPN 280, switching/load balancing 284, Domain NameService resolution 286, acceleration 288 and an application firewall290. In some embodiments, the vServer 275 establishes a connection to aservice 270 of a server 106. The service 275 may comprise any program,application, process, task or set of executable instructions capable ofconnecting to and communicating to the appliance 200, client 102 orvServer 275. For example, the service 275 may comprise a web server,http server, ftp, email or database server. In some embodiments, theservice 270 is a daemon process or network driver for listening,receiving and/or sending communications for an application, such asemail, database or an enterprise application. In some embodiments, theservice 270 may communicate on a specific IP address, or IP address andport.

In some embodiments, the vServer 275 applies one or more policies of thepolicy engine 236 to network communications between the client 102 andserver 106. In one embodiment, the policies are associated with aVServer 275. In another embodiment, the policies are based on a user, ora group of users. In yet another embodiment, a policy is global andapplies to one or more vServers 275 a-275 n, and any user or group ofusers communicating via the appliance 200. In some embodiments, thepolicies of the policy engine have conditions upon which the policy isapplied based on any content of the communication, such as internetprotocol address, port, protocol type, header or fields in a packet, orthe context of the communication, such as user, group of the user,vServer 275, transport layer connection, and/or identification orattributes of the client 102 or server 106.

In other embodiments, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to access the computingenvironment 15, application, and/or data file from a server 106. Inanother embodiment, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to have the application deliverysystem 190 deliver one or more of the computing environment 15,application, and/or data file. In yet another embodiment, the appliance200 establishes a VPN or SSL VPN connection based on the policy engine's236 authentication and/or authorization of a remote user or a remoteclient 103 In one embodiment, the appliance 102 controls the flow ofnetwork traffic and communication sessions based on policies of thepolicy engine 236. For example, the appliance 200 may control the accessto a computing environment 15, application or data file based on thepolicy engine 236.

In some embodiments, the vServer 275 establishes a transport layerconnection, such as a TCP or UDP connection with a client 102 via theclient agent 120. In one embodiment, the vServer 275 listens for andreceives communications from the client 102. In other embodiments, thevServer 275 establishes a transport layer connection, such as a TCP orUDP connection with a client server 106. In one embodiment, the vServer275 establishes the transport layer connection to an internet protocoladdress and port of a server 270 running on the server 106. In anotherembodiment, the vServer 275 associates a first transport layerconnection to a client 102 with a second transport layer connection tothe server 106. In some embodiments, a vServer 275 establishes a pool oftranport layer connections to a server 106 and multiplexes clientrequests via the pooled transport layer connections.

In some embodiments, the appliance 200 provides a SSL VPN connection 280between a client 102 and a server 106. For example, a client 102 on afirst network 102 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104′ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, the clientagent 120 intercepts communications of the client 102 on the firstnetwork 104, encrypts the communications, and transmits thecommunications via a first transport layer connection to the appliance200. The appliance 200 associates the first transport layer connectionon the first network 104 to a second transport layer connection to theserver 106 on the second network 104. The appliance 200 receives theintercepted communication from the client agent 102, decrypts thecommunications, and transmits the communication to the server 106 on thesecond network 104 via the second transport layer connection. The secondtransport layer connection may be a pooled transport layer connection.As such, the appliance 200 provides an end-to-end secure transport layerconnection for the client 102 between the two networks 104, 104′.

In one embodiment, the appliance 200 hosts an intranet internet protocolor intranetIP 282 address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 200,the appliance 200 establishes, assigns or otherwise provides anIntranetIP, which is network identifier, such as IP address and/or hostname, for the client 102 on the second network 104′. The appliance 200listens for and receives on the second or private network 104′ for anycommunications directed towards the client 102 using the client'sestablished IntranetIP 282. In one embodiment, the appliance 200 acts asor on behalf of the client 102 on the second private network 104. Forexample, in another embodiment, a vServer 275 listens for and respondsto communications to the IntranetIP 282 of the client 102. In someembodiments, if a computing device 100 on the second network 104′transmits a request, the appliance 200 processes the request as if itwere the client 102. For example, the appliance 200 may respond to aping to the client's IntranetIP 282. In another example, the appliancemay establish a connection, such as a TCP or UDP connection, withcomputing device 100 on the second network 104 requesting a connectionwith the client's IntranetIP 282.

In some embodiments, the appliance 200 provides one or more of thefollowing acceleration techniques 288 to communications between theclient 102 and server 106: 1) compression; 2) decompression; 3)Transmission Control Protocol pooling; 4) Transmission Control Protocolmultiplexing; 5) Transmission Control Protocol buffering; and 6)caching.

In one embodiment, the appliance 200 relieves servers 106 of much of theprocessing load caused by repeatedly opening and closing transportlayers connections to clients 102 by opening one or more transport layerconnections with each server 106 and maintaining these connections toallow repeated data accesses by clients via the Internet. This techniqueis referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 200 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction is required.For example, in the case of an in-bound packet (that is, a packetreceived from a client 102), the source network address of the packet ischanged to that of an output port of appliance 200, and the destinationnetwork address is changed to that of the intended server. In the caseof an outbound packet (that is, one received from a server 106), thesource network address is changed from that of the server 106 to that ofan output port of appliance 200 and the destination address is changedfrom that of appliance 200 to that of the requesting client 102. Thesequence numbers and acknowledgment numbers of the packet are alsotranslated to sequence numbers and acknowledgement expected by theclient 102 on the appliance's 200 transport layer connection to theclient 102. In some embodiments, the packet checksum of the transportlayer protocol is recalculated to account for these translations.

In another embodiment, the appliance 200 provides switching orload-balancing functionality 284 for communications between the client102 and server 106. In some embodiments, the appliance 200 distributestraffic and directs client requests to a server 106 based on layer 4 orapplication-layer request data. In one embodiment, although the networklayer or layer 2 of the network packet identifies a destination server106, the appliance 200 determines the server 106 to distribute thenetwork packet by application information and data carried as payload ofthe transport layer packet. In one embodiment, the health monitoringprograms 216 of the appliance 200 monitor the health of servers todetermine the server 106 for which to distribute a client's request. Insome embodiments, if the appliance 200 detects a server 106 is notavailable or has a load over a predetermined threshold, the appliance200 can direct or distribute client requests to another server 106.

In some embodiments, the appliance 200 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts' a DNSrequest transmitted by the client 102. In one embodiment, the appliance200 responds to a client's DNS request with an IP address of or hostedby the appliance 200. In this embodiment, the client 102 transmitsnetwork communication for the domain name to the appliance 200. Inanother embodiment, the appliance 200 responds to a client's DNS requestwith an IP address of or hosted by a second appliance 200′. In someembodiments, the appliance 200 responds to a client's DNS request withan IP address of a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 200 provides applicationfirewall functionality 290 for communications between the client 102 andserver 106. In one embodiment, the policy engine 236 provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall 290 protects against denial of service (DoS)attacks. In other embodiments, the appliance inspects the content ofintercepted requests to identify and block application-based attacks. Insome embodiments, the rules/policy engine 236 comprises one or moreapplication firewall or security control policies for providingprotections against various classes and types of web or Internet basedvulnerabilities, such as one or more of the following: 1) bufferoverflow, 2) CGI-BIN parameter manipulation, 3) form/hidden fieldmanipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)broken access control list (ACLs) or weak passwords, 7) cross-sitescripting (XSS), 8) command injection, 9) SQL injection, 10) errortriggering sensitive information leak, 11) insecure use of cryptography,12) server misconfiguration, 13) back doors and debug options, 14)website defacement, 15) platform or operating systems vulnerabilities,and 16) zero-day exploits. In an embodiment, the application firewall290 provides HTML form field protection in the form of inspecting oranalyzing the network communication for one or more of the following: 1)required fields are returned, 2) no added field allowed, 3) read-onlyand hidden field enforcement, 4) drop-down list and radio button fieldconformance, and 5) form-field max-length enforcement. In someembodiments, the application firewall 290 ensures cookies are notmodified. In other embodiments, the application firewall 290 protectsagainst forceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall 290 protectsany confidential information contained in the network communication. Theapplication firewall 290 may inspect or analyze any networkcommunication in accordance with the rules or polices of the engine 236to identify any confidential information in any field of the networkpacket. In some embodiments, the application firewall 290 identifies inthe network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay comprise these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall 290 maytake a policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall 290 may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

C. Client Agent

Referring now to FIG. 3, an embodiment of the client agent 120 isdepicted. The client 102 includes a client agent 120 for establishingand exchanging communications with the appliance 200 and/or server 106via a network 104. In brief overview, the client 102 operates oncomputing device 100 having an operating system with a kernel mode 302and a user mode 303, and a network stack 310 with one or more layers 310a-310 b. The client 102 may have installed and/or execute one or moreapplications. In some embodiments, one or more applications maycommunicate via the network stack 310 to a network 104. One of theapplications, such as a web browser, may also include a first program322. For example, the first program 322 may be used in some embodimentsto install and/or execute the client agent 120, or any portion thereof.The client agent 120 includes an interception mechanism, or interceptor350, for intercepting network communications from the network stack 310from the one or more applications.

The network stack 310 of the client 102 may comprise any type and formof software, or hardware, or any combinations thereof, for providingconnectivity to and communications with a network. In one embodiment,the network stack 310 comprises a software implementation for a networkprotocol suite. The network stack 310 may comprise one or more networklayers, such as any networks layers of the Open Systems Interconnection(OSI) communications model as those skilled in the art recognize andappreciate. As such, the network stack 310 may comprise any type andform of protocols for any of the following layers of the OSI model: 1)physical link layer, 2) data link layer, 3) network layer, 4) transportlayer, 5) session layer, 6) presentation layer, and 7) applicationlayer. In one embodiment, the network stack 310 may comprise a transportcontrol protocol (TCP) over the network layer protocol of the internetprotocol (IP), generally referred to as TCP/IP. In some embodiments, theTCP/IP protocol may be carried over the Ethernet protocol, which maycomprise any of the family of IEEE wide-area-network (WAN) orlocal-area-network (LAN) protocols, such as those protocols covered bythe IEEE 802.3. In some embodiments, the network stack 310 comprises anytype and form of a wireless protocol, such as IEEE 802.11 and/or mobileinternet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIFS) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 310 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 310, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 310 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 310 may be customized, modified or adapted to provide acustom or modified portion of the network stack 310 in support of any ofthe techniques described herein. In other embodiments, the accelerationprogram 120 is designed and constructed to operate with or work inconjunction with the network stack 310 installed or otherwise providedby the operating system of the client 102.

The network stack 310 comprises any type and form of interfaces forreceiving, obtaining, providing or otherwise accessing any informationand data related to network communications of the client 102. In oneembodiment, an interface to the network stack 310 comprises anapplication programming interface (API). The interface may also compriseany function call, hooking or filtering mechanism, event or call backmechanism, or any type of interfacing technique. The network stack 310via the interface may receive or provide any type and form of datastructure, such as an object, related to functionality or operation ofthe network stack 310. For example, the data structure may compriseinformation and data related to a network packet or one or more networkpackets. In some embodiments, the data structure comprises a portion ofthe network packet processed at a protocol layer of the network stack310, such as a network packet of the transport layer. In someembodiments, the data structure 325 comprises a kernel-level datastructure, while in other embodiments, the data structure 325 comprisesa user-mode data structure. A kernel-level data structure may comprise adata structure obtained or related to a portion of the network stack 310operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 310 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 310. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 310 to an application while a second portion 310 a of the networkstack 310 provides access to a network. In some embodiments, a firstportion 310 a of the network stack may comprise one or more upper layersof the network stack 310, such as any of layers 5-7. In otherembodiments, a second portion 310 b of the network stack 310 comprisesone or more lower layers, such as any of layers 1-4. Each of the firstportion 310 a and second portion 310 b of the network stack 310 maycomprise any portion of the network stack 310, at any one or morenetwork layers, in user-mode 203, kernel-mode, 202, or combinationsthereof, or at any portion of a network layer or interface point to anetwork layer or any portion of or interface point to the user-mode 203and kernel-mode 203.

The interceptor 350 may comprise software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercept a network communication at any point in the network stack 310,and redirects or transmits the network communication to a destinationdesired, managed or controlled by the interceptor 350 or client agent120. For example, the interceptor 350 may intercept a networkcommunication of a network stack 310 of a first network and transmit thenetwork communication to the appliance 200 for transmission on a secondnetwork 104. In some embodiments, the interceptor 350 comprises any typeinterceptor 350 comprises a driver, such as a network driver constructedand designed to interface and work with the network stack 310. In someembodiments, the client agent 120 and/or interceptor 350 operates at oneor more layers of the network stack 310, such as at the transport layer.In one embodiment, the interceptor 350 comprises a filter driver,hooking mechanism, or any form and type of suitable network driverinterface that interfaces to the transport layer of the network stack,such as via the transport driver interface (TDI). In some embodiments,the interceptor 350 interfaces to a first protocol layer, such as thetransport layer and another protocol layer, such as any layer above thetransport protocol layer, for example, an application protocol layer. Inone embodiment, the interceptor 350 may comprise a driver complying withthe Network Driver Interface Specification (NDIS), or a NDIS driver. Inanother embodiment, the interceptor 350 may comprise a min-filter or amini-port driver. In one embodiment, the interceptor 350, or portionthereof, operates in kernel-mode 202. In another embodiment, theinterceptor 350, or portion thereof, operates in user-mode 203. In someembodiments, a portion of the interceptor 350 operates in kernel-mode202 while another portion of the interceptor 350 operates in user-mode203. In other embodiments, the client agent 120 operates in user-mode203 but interfaces via the interceptor 350 to a kernel-mode driver,process, service, task or portion of the operating system, such as toobtain a kernel-level data structure 225. In further embodiments, theinterceptor 350 is a user-mode application or program, such asapplication.

In one embodiment, the interceptor 350 intercepts any transport layerconnection requests. In these embodiments, the interceptor 350 executetransport layer application programming interface (API) calls to set thedestination information, such as destination IP address and/or port to adesired location for the location. In this manner, the interceptor 350intercepts and redirects the transport layer connection to a IP addressand port controlled or managed by the interceptor 350 or client agent120. In one embodiment, the interceptor 350 sets the destinationinformation for the connection to a local IP address and port of theclient 102 on which the client agent 120 is listening. For example, theclient agent 120 may comprise a proxy service listening on a local IPaddress and port for redirected transport layer communications. In someembodiments, the client agent 120 then communicates the redirectedtransport layer communication to the appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may comprise two agents120 and 120′. In one embodiment, a first agent 120 may comprise aninterceptor 350 operating at the network layer of the network stack 310.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 310. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 310 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 310 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor may operate at orinterface with the network stack 310 in a manner transparent to anyapplication, a user of the client 102, and any other computing device,such as a server, in communications with the client 102. The clientagent 120 and/or interceptor 350 may be installed and/or executed on theclient 102 in a manner without modification of an application. In someembodiments, the user of the client 102 or a computing device incommunications with the client 102 are not aware of the existence,execution or operation of the client agent 120 and/or interceptor 350.As such, in some embodiments, the client agent 120 and/or interceptor350 is installed, executed, and/or operated transparently to anapplication, user of the client 102, another computing device, such as aserver, or any of the protocol layers above and/or below the protocollayer interfaced to by the interceptor 350.

The client agent 120 includes an acceleration program 302, a streamingclient 306, and/or a collection agent 304. In one embodiment, the clientagent 120 comprises an Independent Computing Architecture (ICA) client,or any portion thereof, developed by Citrix Systems, Inc. of FortLauderdale, Fla., and is also referred to as an ICA client. In someembodiments, the client 120 comprises an application streaming client306 for streaming an application from a server 106 to a client 102. Insome embodiments, the client agent 120 comprises an acceleration program302 for accelerating communications between client 102 and server 106.In another embodiment, the client agent 120 includes a collection agent304 for performing end-point detection/scanning and collecting end-pointinformation for the appliance 200 and/or server 106.

In some embodiments, the acceleration program 302 comprises aclient-side acceleration program for performing one or more accelerationtechniques to accelerate, enhance or otherwise improve a client'scommunications with and/or access to a server 106, such as accessing anapplication provided by a server 106. The logic, functions, and/oroperations of the executable instructions of the acceleration program302 may perform one or more of the following acceleration techniques: 1)multi-protocol compression, 2) transport control protocol pooling, 3)transport control protocol multiplexing, 4) transport control protocolbuffering, and 5) caching via a cache manager Additionally, theacceleration program 302 may perform encryption and/or decryption of anycommunications received and/or transmitted by the client 102. In someembodiments, the acceleration program 302 performs one or more of theacceleration techniques in an integrated manner or fashion.Additionally, the acceleration program 302 can perform compression onany of the protocols, or multiple-protocols, carried as payload ofnetwork packet of the transport layer protocol The streaming client 306comprises an application, program, process, service, task or executableinstructions for receiving and executing a streamed application from aserver 106. A server 106 may stream one or more application data filesto the streaming client 306 for playing, executing or otherwise causingto be executed the application on the client 102. In some embodiments,the server 106 transmits a set of compressed or packaged applicationdata files to the streaming client 306. In some embodiments, theplurality of application files are compressed and stored on a fileserver within an archive file such as a CAB, ZIP, SIT, TAR, JAR or otherarchives In one embodiment, the server 106 decompresses, unpackages orunarchives the application files and transmits the files to the client102. In another embodiment, the client 102 decompresses, unpackages orunarchives the application files. The streaming client 306 dynamicallyinstalls the application, or portion thereof, and executes theapplication. In one embodiment, the streaming client 306 may be anexecutable program. In some embodiments, the streaming client 306 may beable to launch another executable program.

The collection agent 304 comprises an application, program, process,service, task or executable instructions for identifying, obtainingand/or collecting information about the client 102. In some embodiments,the appliance 200 transmits the collection agent 304 to the client 102or client agent 120. The collection agent 304 may be configuredaccording to one or more policies of the policy engine 236 of theappliance. In other embodiments, the collection agent 304 transmitscollected information on the client 102 to the appliance 200. In oneembodiment, the policy engine 236 of the appliance 200 uses thecollected information to determine and provide access, authenticationand authorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 comprises an end-pointdetection and scanning mechanism, which identifies and determines one ormore attributes or characteristics of the client. For example, thecollection agent 304 may identify and determine any one or more of thefollowing client-side attributes: 1) the operating system an/or aversion of an operating system, 2) a service pack of the operatingsystem, 3) a running service, 4) a running process, and 5) a file. Thecollection agent 304 may also identify and determine the presence orversions of any one or more of the following on the client: 1) antivirussoftware, 2) personal firewall software, 3) anti-spam software, and 4)internet security software. The policy engine 236 may have one or morepolicies based on any one or more of the attributes or characteristicsof the client or client-side attributes.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or portionthereof, such as the interceptor 350, automatically, silently,transparently, or otherwise. In one embodiment, the first program 322comprises a plugin component, such an ActiveX control or Java control orscript that is loaded into and executed by an application. For example,the first program comprises an ActiveX control loaded and run by a webbrowser application, such as in the memory space or context of theapplication. In another embodiment, the first program 322 comprises aset of executable instructions loaded into and run by the application,such as a browser. In one embodiment, the first program 322 comprises adesigned and constructed program to install the client agent 120. Insome embodiments, the first program 322 obtains, downloads, or receivesthe client agent 120 via the network from another computing device. Inanother embodiment, the first program 322 is an installer program or aplug and play manager for installing programs, such as network drivers,on the operating system of the client 102.

D. Efficient SSL handshake processing

Referring now to FIG. 4A, a flow diagram of an example SSL handshake isshown. In brief overview, a client 102 transmits a client hello message401. An appliance 200 may then respond with a server hello 403, servercertificate 405, client certificate request 407, and server hello donemessages 409. The client may then respond with a client key exchangemessage 413, a client change cipher message 415, and a client finishmessage 417. The appliance 200 may then respond with a server changecipher message 419, and a server finish message 421. In some SSLhandshakes, in response to the server's Certificate Request message, theclient may send a Client Certificate message followed by a client keyexchange message 413, a client-certificate-verify message, aclient-change-cipher message 415 and a client finish message 417.

Still referring to FIG. 4A, now in greater detail, a client 102 and anappliance 200 engage in an SSL handshake. An SSL handshake may beperformed according to any version of SSL including without limitationSSLv2 and SSLv3.0. An SSL handshake may also be performed according toany related secure communication standards including without limitationTLS 1.0 as defined in RFC 2246 and TLS 1.1 as defined in RFC 4346.Additional published documents describing related protocols andextensions to SSL and TLS which may be used in conjunction with themethods described below include without limitation RFC 2712, RFC 2817,RFC 2818, RFC 3268, RFC 3546, RFC 4132, RFC 4162, RFC 4279, RFC 4347,RFC 4366, and RFC 4492.

In one embodiments, an appliance may initiate perform an SSL handshakeas a client. For example, an appliance may initiate an SSL connectionwith a server, or with a second appliance. In this embodiment, theappliance may send the client hello message 401, client certificatemessage 411, a client key exchange message 413, a client change ciphermessage 415, and a client finish message 417. In this embodiment, theappliance may also send a client certificate message followed by aclient key exchange message 413, a client-certificate-verify message, aclient-change-cipher message 415 and a client finish message 417.

In another embodiment, an abbreviated SSL handshake may be used toresume a previous session. In another embodiment, an SSL handshake mayalso include server verification of a client, such as via transmissionfrom the client to the server of a client certificate and a clientcertificate verify message.

An SSL handshake may require a message digest be computed of all themessages exchanged in order to verify that an SSL server and SSL clienthave received the same messages, and no errors or attacks have beenintroduced into the transmissions. To perform the verification, a clientmay first compute a message digest of all the messages the SSL clienthas sent and received comprising the handshake, and then transmit theresult to the SSL server via a client finish message 417. The SSL servermay then compute the message digest of all messages the SSL server hassent and received in order to verify that the two message digests arethe same. The SSL client and SSL server may compute the message digestusage digest algorithm agreed upon during the course of the handshake.Examples of message digest algorithms may include without limitationMD4; MD5; CRC-32; MD5; RIPEMD-160; SHA; and HAVAL.

Referring now to FIG. 4B, a flow diagram of an appliance utilizing bulkdecryption is shown. In brief overview, an appliance 200 receives aplurality of encrypted data packets. The appliance buffers a pluralityof the data packets in one or more buffers 440 a. The appliance may thenprovide a plurality of buffered data packets to an cryptographicprocessing card 450 for decryption. The appliance may then process thedecrypted data.

Still referring to FIG. 4B, now in greater detail, an appliance 200receives a plurality of encrypted data packets. The encrypted packetsmay be received from any computing device, including a client 102,server 106, or a second appliance 200.

The encrypted packets may be encrypted using any encryption algorithm,including without limitation RSA, DES, DES3, AES, Blowfish, IDEA, SEAL,and RC4. The packets may comprise any protocol described herein. In someembodiments, the encrypted data may comprise one or more SSL records. Insome embodiments the encrypted packets may be received from a pluralityof sources. In some embodiments, the encrypted packets may be receivedfrom a plurality of connections.

The received encrypted packets may then be buffered in one or morebuffers 440 a. In some embodiments, the buffers 440 a may be a fixedsize. In other embodiments, the buffers 440 b may be a variable size. Insome embodiments, a given buffer may be assigned to a given connection.In other embodiments, a buffer may receive data from a plurality ofconnections.

The received encrypted packets may be buffered until a complete SSLrecord has been received. An SSL record may comprise a header, data, amessage authentication code, and any necessary padding. The SSL headermay comprise a type field, a version field, and a length field. In somecases, portions of a single SSL record may be encapsulated in aplurality of packets. In other cases, a single packet may compriseportions of a plurality of SSL records.

Upon receipt of a complete SSL record, the buffer may provide the SSLrecord to the cryptographic processing card 450. A cryptographicprocessing card may comprise any hardware specifically designed oradapted to compute cryptographic functions such as message digests,including without limitation the OCTEON and NITROX lines of securityprocessors and acceleration boards manufactured by Cavium Networks, andthe BCM1600, BCM4000, BCM5820 and other security and SSL processorsmanufactured by Broadcom Corporation. In some embodiments, an appliancemay comprise a plurality of dedicated cryptographic processing cards.

In some embodiments, the SSL record may be passed to the cryptographicprocessing card 450. In other embodiments, the lengths and locations ofthe SSL record within the buffer may be provided to the card. In somecases, portions of a single SSL record may be stored in more than onebuffer. In these cases, the locations of the SSL record within the morethan one buffers may be provided to the card.

In some embodiments, the cryptographic processing card 450 may decryptan SSL record in-place, writing over the encrypted data with thedecrypted data. In this manner, the same buffer or buffers is used tohold the decrypted data as was used to hold the encrypted data. In otherembodiments, the cryptographic processing card 450 may decrypt an SSLrecord and store the decrypted data in a different buffer or memoryelement. The appliance may then process the decrypted data in accordancewith performing any of the appliance functions described herein.

Referring now to FIG. 4C, a flow diagram of an appliance providing bulkencryption is shown. In brief overview, unencrypted data that has beenprocessed or received by the appliance is buffered prior totransmission. Upon the occurrence of a transmission condition, thebuffered data is provided to a cryptographic processing card 450 forencryption. The encrypted data is then transmitted.

Still referring to FIG. 4C, now in greater detail, unencrypted data thathas been processed or received by the appliance is buffered prior totransmission. In some embodiments, the unencrypted data may compriseunencrypted data previously received by the appliance. In otherembodiments, the unencrypted data may comprise encrypted data previouslyreceived by the appliance and subsequently decrypted. In one embodiment,the unencrypted data may comprise encrypted data previously received bythe appliance and subsequently decrypted by the appliance using a bulkdecryption method as described herein.

The unencrypted data may be stored in one or more buffers 440 b until atransmission condition is met. Transmission conditions, which in bediscussed in greater detail in conjunction with FIG. 7, may include anyof the following (i) a given quantum size of unencrypted data beingreceived in the buffer, (ii) an end-of-transaction message in theunencrypted data, (iii) a FIN message in the unencrypted data, (iv) aTCP PUSH message in the unencrypted data, and (v) a timer expiring.

After the occurrence of a transmission condition, the bufferedunencrypted data is passed to a cryptographic processing card 450 forencryption. The encryption process may utilize any encryption algorithm.In one embodiment, a single SSL record will be created from theencrypted data. The encrypted data is then transmitted.

Referring now to FIG. 5, a flow diagram of a method for buffering SSLhandshake messages prior to efficiently computing a message digest forthe SSL handshake is shown. In brief overview, the method comprises:conducting, by an appliance with a client, an SSL handshake, the SSLhandshake comprising a plurality of SSL handshake messages (step 501);storing, by the appliance, the plurality of SSL handshake messages (step503); providing, by the appliance to a message digest computing devicein response to receiving a client finish message, the plurality of SSLhandshake messages (step 505); receiving, by the appliance from themessage digest computing device, a message digest corresponding to theprovided messages (step 507); determining by the appliance, the messagedigest matches a message digest included in the SSL client finishmessage (step 509); and completing, by the appliance with the client,the SSL handshake (step 511).

Still referring to FIG. 5, now in greater detail, a method for bufferingSSL handshake messages prior to computing a message digest for the SSLhandshake comprises: conducting, by an appliance 200 with a client, anSSL handshake, the SSL handshake comprising a plurality of SSL handshakemessages (step 501). The appliance 200 may conduct the SSL handshakeusing any of the SSL, TLS, and related protocols described herein. Insome embodiments, the appliance 200 may initiate the SSL handshake. Inother embodiments, the appliance 200 may receive a handshake initiationrequest. The plurality of SSL handshake messages may comprise any of theSSL handshake messages described. In some embodiments, the SSL handshakemay comprise a session re-use or resume handshake. In some embodiments,the plurality of SSL handshake messages may comprise a subset of themessage comprising the conducted SSL handshake.

An appliance may then store the plurality of SSL handshake messages(step 503). In some embodiments, the appliance 200 may store allmessages comprising the SSL handshake record, including at least one of:a client hello message, a server hello message, and a client keyexchange message, a client certificate message, a client certificateverify message, a server certificate message and a client certificaterequest message, and a server hello done message.

In some embodiments, the appliance 200 the stored plurality of SSLhandshake messages may comprise a subset of the SSL handshake messagescomprising the handshake record. In one embodiment, the appliance maystore only received messages and those sent messages which cannot beregenerated by the appliance. An example of a sent message which may notbe able to be regenerated may be the server hello message, whichincludes a random component comprising the session identifier. Forexample, in an embodiment where the appliance 200 is acting as the SSLserver, the appliance 200 may store the client hello, server hello, andclient key exchange messages. The appliance may then regenerate theserver certificate, server hello done, and client certificate requestmessages for purposes of computing the message digest.

In some embodiments, the appliance may store only a portion of amessage, and then regenerate the rest of the message when computing themessage digest. For example, in an embodiment where the appliance 200 isacting as the SSL client, the appliance may store the random componentof a sent client hello message in a data structure comprising otherinformation about the SSL connection request such as the server address,and then regenerate the client hello message using the stored portionand the other information for purposes of computing the message digest.

In some embodiments, the appliance may store the plurality of messagesin a separate buffer corresponding to the SSL handshake. In anotherembodiment, the appliance may store the plurality of messages in thebuffers in which the messages were received or sent. In thisembodiments, the appliance 200 may maintain a data structure indicatingthe lengths and locations of the messages. In some embodiments, some ofthe plurality of messages may be stored in memory dedicated toprecomputed handshake messages, as will be discussed in conjunction withFIG. 6.

After storing the plurality of SSL handshake messages (step 503), theappliance may provide, by the appliance to a message digest computingdevice in response to receiving a client finish message, the pluralityof SSL handshake messages (step 505). A message digest computing devicemay comprise any processor, card, or circuitry, or other hardwarecapable of computing a message digest. In one embodiment, a messagedigest computing device may comprise a general purpose microprocessor.In some embodiments, the message digest computing device may be locatedwithin the physical appliance 200. In other embodiments, the messagedigest computing device may be a separate standalone device.

In one embodiment, the message digest computing device may comprise adedicated cryptographic processing card 450 located within theappliance. In some embodiments, an appliance may comprise a plurality ofdedicated cryptographic processing cards. In one embodiment theappliance may determine which of a plurality of dedicated cryptographicprocessing cards 450 to provide the SSL handshake messages to based onone or more load balancing factors, including without limitationavailability, capacity, latency, and current usage.

In some embodiments, the appliance may pass the plurality of SSLhandshake messages to the message digest computing device. In otherembodiments, the appliance may pass the lengths and locations of themessages to the message digest computing device. The appliance may alsospecify the algorithm to be used by the message digest computing deviceto compute the message digest.

In some embodiments, the appliance may provide additional messages alongwith the stored plurality of SSL handshake messages to be included inthe message digest computation. In embodiments where only a subset ofthe SSL handshake messages were stored, the appliance may regenerate theSSL handshake messages not stored, and provide the regenerated messagesalong with the stored plurality of messages to the message digestcomputing device. For example, in an embodiment where the appliance 200is acting as the SSL server, the appliance 200 may store the clienthello, server certificate, server hello done, and client key exchangemessages corresponding to a given SSL handshake, and store portions ofthe server hello message. Upon receiving the client finish message, theappliance may then regenerate the server hello message. The appliancemay then provide the message digest computing device with the lengthsand locations of the client hello, server hello, and, servercertificate, server hello done, and client key exchange messages , andclient certificate request messages. The message digest computer maythen compute a single message digest corresponding to all of the SSLhandshake messages.

After providing, by the appliance to a message digest computing devicein response to receiving a client finish message, the plurality of SSLhandshake messages (step 505); the appliance may receive, from themessage digest computing device, a message digest corresponding to theprovided messages (step 507). In some embodiments, the message digestcomputing device may pass the message digest to the appliance. In otherembodiments, the message digest computing device may provide theappliance with a location where the message digest is stored in memory.

After receiving, from the message digest computing device, a messagedigest corresponding to the provided messages (step 507); the appliancemay then determine the message digest matches a message digest includedin the SSL client finish message (step 509). In the event the messagedigest does not match a message digest included in the SSL client finishmessage, the appliance may follow any SSL protocol or take any actioncorresponding to a potentially corrupted or failed handshake, includingwithout limitation transmitting a handshake failure message, restartingthe handshake, or disconnecting from the client.

After determining by the appliance, the message digest matches a messagedigest included in the SSL client finish message (step 509); theappliance may complete, with the client, the SSL handshake (step 511).The SSL handshake may be completed according to any SSL protocol,including without limitation the transmission of an SSL server finishmessage. After completion of the SSL handshake, the appliance and theclient may then begin transmitting data via the established SSL channel.

In some embodiments, the above method may be used to maximize availableappliance CPU time. For example, the method may require less CPU cyclesthan an alternative method of progressively updating the message digestfor the SSL handshake each time an SSL handshake messages is received orsent.

In other embodiments, the above method may be utilized to maximizethroughput for a message digest computing device. For example, anappliance may have a dedicated cryptographic processing card with agiven capacity for computing message digests. By storing the SSLhandshake messages and computing the message digest only at the end ofthe handshake, an appliance may be able to access the card fewer times,while still handling the same number of transactions. In someembodiments, accessing the card fewer times may result in increasednumber of SSL handshakes that can be processed over a given interval. Inother embodiments, accessing the card fewer times may free the card toperform cryptographic operations for other appliance functions, such asencrypting or decrypting messages.

In some embodiments, this method may allow an appliance to reach andoptimize the maximum number of operations per second of a givendedicated cryptographic processing card. For example, if a given cardhas a maximum throughput of 8000, 12,000, or 20,000 cryptographicoperations per second, using the described method may result in more SSLhandshakes being completed per second, as opposed to the method whereinthe message digest is computed serially, and the card must be accessedmultiple times to compute message digests during the course of an SSLhandshake.

In some embodiments, the above method may allow an appliance to handleincreased SSL transactions per second. The above method may result inperformance gains of 5%, 10%, 15%, 20%, 25%, 30% or more when used incomparison to an appliance with identical hardware computing SSLhandshake message digests in a serial manner.

Referring now to FIG. 6, a method for enabling efficient SSL handshakesthrough precomputing of handshake messages is shown. In brief overview,the method comprises: receiving, by an appliance, a server certificateidentifying a server (step 601); generating, by the appliance, at leastone of: (i) an SSL server certificate message comprising the receivedserver certificate, (ii) an SSL client certificate request message, and(iii) an SSL hello done message (step 603); storing, by the appliance,the generated messages (step 605); receiving, by the appliance from aclient, an SSL client hello message identifying the server (step 607);and transmitting, by the appliance to the client, an SSL server hellomessage and at least one of the stored messages (step 609).

Still referring to FIG. 6, now in greater detail, a method for enablingefficient SSL handshakes through precomputing of handshake messagescomprises receiving, by an appliance, a server certificate identifying aserver (step 601). The server certificate may comprise any type ofcertificate used to authenticate a computing device, including withoutlimitation an X509v3 certificate. The server certificate may correspondto any computing device capable of communicating with the appliance 200,including a server 106, a second appliance 200, or a client 102.

The appliance 200 may receive the server certificate via any means. Inone embodiment, the server certificate may be transferred to theappliance during configuration of the appliance. During configuration,the appliance may receive instructions from an administrator associatinga given server certificate with a given network address. In oneembodiment, an appliance may be configured with server certificates foreach of a plurality of servers to which the appliance provides access.In another embodiment, upon startup of the appliance, the appliance mayrequest server certificates from servers 106 connected to the appliance200 via a local area network. The appliance may then receive, verify,and store the server certificates.

After receiving, a server certificate identifying a server (step 601);the appliance may generate, at least one of: (i) an SSL servercertificate message comprising the received server certificate, (ii) anSSL client certificate request message, and (iii) an SSL hello donemessage (step 603). In one embodiment, the appliance may generate themessages prior to receiving an SSL client hello requesting an SSLconnection with the server identified by the server certificate. Inanother embodiment, the appliance may generate the messages in responseto a single SSL client hello request, and then store the messages forresponding to future request. The messages generated may be generatedprior to the initiation of an SSL handshake since they do not depend oneither random factors contained in previous handshake message orinformation corresponding to the client requesting the connection. Themessages may be generated in any way, and be generated according to anyof the SSL and TSL protocols described herein.

In other embodiments, any other SSL handshake messages which do notdepend on the identity of the other party or previously transmittedhandshake message be generated prior to an SSL handshake and stored. Forexample, if an appliance is functioning as an SSL client, the appliancemay generate a client certificate message corresponding to a receivedcertificate prior to initiating an SSL handshake.

After generating the messages (step 603); the appliance may store thegenerated messages (step 605). The generated messages may be stored inany form, in any data structure, and in any memory element. In oneembodiment, the generated messages may be stored in a data structurecorresponding to the server identified by the server certificate. Inanother embodiment, the generated messages may be stored in a datastructure which allows the generated messages to efficiently beretrieved and transmitted to a client.

After storing the generated messages (step 605); the appliance mayreceive, from a client, an SSL client hello message identifying theserver (step 607). The appliance may determine that the client helloidentifies the server by any means, including by consulting a table orlist of servers for which the appliances has previously generatedhandshake messages, or by consulting a data structure corresponding tothe identified server to determine whether handshake messages havepreviously been generated.

After receiving, from a client, an SSL client hello message identifyingthe server (step 607); the appliance may transmit, to the client, an SSLserver hello message and at least one of the stored messages (step 609).These messages may be transmitted according to any of the SSL and TSLprotocols described herein.

In one embodiment, two or more of the stored messages may be transmittedin a single transport layer packet. In another embodiment, two or moreof the stored messages may be transmitted in a single network layerpacket. In yet another embodiment, the appliance may transmit in asignle transport layer or network layer packet (i) a previously storedSSL server certificate message comprising the received servercertificate, (ii) an SSL client certificate request message, and (iii)an SSL hello done message. In other embodiments, one or more of thestored messages may be transmitted in a single transport layer packetwith the server hello message.

As an illustrative example, during configuration of an appliance, anadministrator may transfer a plurality of server certificates to theappliance, each server certificate corresponding to a server to whichthe appliance provides access. The appliance may then, during eitherconfiguration or initial startup, generate for each received certificate(i) an SSL server certificate message comprising the received servercertificate, (ii) an SSL client certificate request message, and (iii)an SSL hello done message for each server certificate. The appliance maythen receive an SSL client hello message identifying one of the serverto which the appliance provides access. Upon receiving the message, theappliance may generate and transmit an SSL server hello message onbehalf of the server. The appliance may then retrieve the three storedmessages corresponding to the identified server's server certificate,and transmit them to the client in a single transport layer packet. Theappliance may then perform any additional steps required to complete theSSL handshake.

In some embodiments, the method of precomputing SSL handshake messagesmay be combined with the above method of buffering SSL handshakemessages to provide more efficiency gains. The tables below provideillustrative examples of how the methods may be combined in a number ofSSL handshake scenarios, utilizing a dedicated cryptographic processingcard.

EXAMPLE 1

Full SSL handshake, appliance acting as SSL server Message ApplianceActions Client Hello → Buffer the Client-Hello message.

Server Hello Form the Server-Hello message and send the message out.Store the 32 byte random part of the Server-Hello and other informationin SSL session data structure.

Server Certificate Retrieve the previously generated Server Certificatemessage from storage. Send the message out.

Server Hello Done Retrieve the previously generated Server Hello Donemessage from storage. Send the message out. Client Key Exchange → Bufferthe Client-Key-Exchange message. Client Change Cipher Specs → Nobuffering for this message. This message is not part of the handshakerecord. Client Finish → Send the start address and lengths of thebuffered messages and generated messages to dedicated cryptographicprocessing card for: 1. Decryption of the Client-Key-Exchange   message. 2. Creation of master-secret and session keys from   pre-master secret. 3. Computation of message digest for SSL   handshake, and/or decryption of client finish    message. 4. Creation ofServer Finish message.

Server Change Cipher Generate message and send out. Specs

Server Finish Retrieve the Server-Finish message from the card and sendout.

EXAMPLE 2

Session resume handshake, appliance acting as SSL server MessageAppliance Actions Client Hello → Buffer the Client-Hello message.

Server Hello Form the Server-Hello message and send the message out.Store the 32 byte random part of the Server-Hello and other informationin SSL session data structure.

Server Change Cipher Generate message and send out. No buffering forthis Specs message. Non-handshake record.

Server Finish Call card function to: 1. Create key-block. 2. CreateServer Finish message. 3. Computation of message digest for SSL   handshake Send the card-generated Server-Finish message out. ClientChange Cipher Specs → No buffering for this message. Non-handshakerecord. Client Finish → Verify predicted Client-Finish (RC4), Or Callcard function to decrypt the Client-Finish (DES/3DES, AES) and verifythe Finish message.

EXAMPLE 3

SSL Handshake using ephemeral RSA keys, appliance acting as SSL serverMessage Appliance Action Client Hello → Buffer the Client-Hello message.

Server Hello Form the Server-Hello message and send the message out.Store the 32 byte random part of the Server-Hello and other informationin SSL session data structure.

Server Certificate Retrieve the previously generated Server Certificatemessage from storage. Send the message out.

Server Key Exchange Form the Server Key Exchange and send the messageout. Use card function to offload RSA_sign operation.

Server Hello Done Retrieve the previously generated Server Hello Donemessage from storage. Send the message out. Client Key Exchange → Bufferthe Client-Key-Exchange message. Client Change Cipher Specs → Nobuffering for this message. Non-handshake record. Client Finish → Sendthe start address and lengths of the buffered messages to card for: 1.Decryption of the Client-Key-Exchange    message. 2. Creation ofmaster-secret and session keys from    pre-master secret. 3. Computationof message digest for SSL    handshake, and/or decryption of clientfinish    message. 4. Creation of Server Finish message.

Server Change Cipher Generate message and send out. No buffering forthis Specs message. Non-handshake record.

Server Finish Send the card generated Server-Finish message out.

EXAMPLE 4

SSL handshake including client authentication, appliance acting as SSLserver Client Hello → Buffer the Client-Hello message.

Server Hello Form the Server-Hello message and send the message out.Store the 32 byte random part of the Server-Hello and other informationin SSL session data structure.

Server Certificate Retrieve the previously generated Server Certificatemessage from storage. Send the message out.

Server Certificate Request Retrieve the previously generated ClientCertificate Request message from storage. Send the message out.

Server Hello Done Retrieve the previously generated Server Hello Donemessage from storage. Send the message out. Client Certificate → Bufferthe Client Certificate message. Client Key Exchange → Buffer theClient-Key-Exchange message. Client Certificate Verify → Buffer theClient Certificate Verify message. Client Change Cipher Specs → Nobuffering for this message. Non-handshake record. Client Finish → Sendthe start address and lengths of the buffered messages to card for: 1.Decrypt Client Certificate verify message and    verify it. 2.Decryption of the Client-Key-Exchange    message. 3. Creation ofmaster-secret and session keys from    pre-master secret. 4. Computationof message digest for SSL    handshake, and/or decryption of clientfinish    message. 5. Creation of Server Finish message.

Server Change Cipher Generate message and send out. No buffering forthis Specs message. Non-handshake record.

Server Finish Send the card generated Server-Finish message out.

EXAMPLE 5

Full SSL Handshake, appliance acting as SSL client Message ApplianceActions Client Hello → Form the Client-Hello message and send themessage out. Store the 32 byte random part of the Client-Hello and otherinformation in SSL session data structur

Server Hello Buffer the Server Hello message.

Server Certificate Buffer the Server Certificate message.

Server Hello Done Buffer the Server Hello Done message. Client KeyExchange → Form the Client-Key-Exchange message Call card function toencrypt the pre-master secret with server's public-key.RSA_private_encrypt. Send the message out. Client Change Cipher Specs →Send this message out. No buffering. Non-handshake record. Client Finish→ Send the start address and lengths of the buffered messages to cardfor: 1. Creation of master-secret and session keys from    pre-mastersecret. 2. Creation of Client Finish message. 3. Computation of messagedigest for SSL    handshake messages

Server Change Cipher No buffering for this message. Non-handshakerecord. Specs

Server Finish Verify the received message with the computed messagedigest, or Call card function to decrypt the received finish message andcompare with computed message digest.

Referring now to FIG. 7, a flow diagram of a method for using a networkappliance to efficiently buffer and encrypt data for transmission isshown. In brief overview, the method comprises: receiving, by anappliance via a connection, a first SSL record, the first recordcomprising a first encrypted message (step 701); decrypting, by theappliance, the first encrypted message to produce a first decryptedmessage (step 703); buffering, by the appliance, the first decryptedmessage (step 705); receiving, by the appliance via the connection, asecond SSL record, the second record comprising a second encryptedmessage (step 707); decrypting, by the appliance, the second encryptedmessage to produce a second decrypted message (step 709); determining,by the appliance, that a transmittal condition has been satisfied (step711); encrypting, by the appliance in response to the determination, thefirst decrypted message and a portion of the second decrypted message toproduce a third SSL record (step 713); and transmitting, by theappliance via a second connection, the third record (step 715).

Still referring to FIG. 7, now in greater detail, an appliance receives,via a connection, a first SSL record, the first record comprising afirst encrypted message (step 701). The connection may be with anycomputing device, including a client 102, server 106, or a secondappliance 200. The SSL record may comprise any SSL or related protocol,including without limitation SSLv2, SSLv3, TLS 1.0 and TLS 1.1. Thefirst encrypted message may be encrypted using any encryption algorithm.

In some embodiments, the first record may be received in a singletransport or network layer packet. In other embodiments, the firstrecord may be received in a plurality of transport or network layerpackets.

After receiving, via a connection, a first SSL record (step 701); theappliance may decrypt the first encrypted message to produce a firstdecrypted message (step 703). In some embodiments, the appliance mayutilize a cryptographic processing card to decrypt the message. In otherembodiments, the appliance may utilize any of the bulk decryptionmethods described herein to decrypt the message.

After decrypting the message (step 703), the appliance may buffer thedecrypted message (step 705). In some embodiments, the appliance mayalso process the decrypted message in the course of performing any ofthe network appliance functions described herein.

The appliance may then receive, via the connection, a second SSL record,the second record comprising a second encrypted message (step 707); anddecrypt the second encrypted message to produce a second decryptedmessage (step 709). These steps may be performed in any mannerpreviously discussed. In some embodiments, these steps may occur inparallel or prior to any of the previous steps. For example, theappliance may receive the second record prior to the completion ofdecrypting the first message. Or, for example, the appliance may receivethe second record immediately after receiving the first record. In someembodiments the appliance may also process the second decrypted messagein the course of performing any of the network appliance functionsdescribed herein.

After decrypting, the second encrypted message to produce a seconddecrypted message (step 709); the appliance may determine that atransmittal condition has been satisfied (step 711). A transmittalconditional may comprise any indication that the messages currentlybuffered should be encrypted and transmitted immediately.

In one embodiment, a transmittal condition may comprise reaching amaximum quantum size. In this embodiment, once a certain number of bytesof decrypted data is ready for transmission, the condition is triggered.A maximum quantum size may be determined with respect to any of thefollowing: (i) a maximum segment size for an outgoing connection, (ii) amaximum input size for a cryptographic processing card, (iii) a maximumbuffer size, and (iv) a maximum SSL record size specified by a protocol.For example, an appliance may receive SSL data from a client, destinedto a server. The appliance may decrypt and process the SSL data in orderto provide various network appliance functions. The appliance may thenbuffer the decrypted data until the amount of data reaches a thresholdcorresponding to the maximum input size of a cryptographic processingcard. The appliance may then send the data to the card for encryptionand then transmit the data to the server.

In another embodiment, a transmittal condition may comprise receiving anend-of-transaction indicator. In one embodiment, the appliance maydetect an end-of-transaction indicator for http or https data passingthrough the appliance. Upon detecting the end-of-transaction indicator,the appliance may send all buffered data corresponding to thetransaction for encryption and transmission.

In another embodiment, a transmittal condition may comprise receiving aFIN indicator for a given connection. For example, an appliance maydetect a TCP FIN packet on a TCP connection the appliance is routingfrom a client to a server. Upon detecting the TCP FIN indicator, theappliance may send all buffered data corresponding to the TCP connectionfor encryption and transmission.

In another embodiment, a transmittal condition may comprise receiving aPUSH indicator for a given connection. For example, an appliance maydetect a TCP PUSH packet on a TCP connection the appliance is routingfrom a client to a server. Upon detecting the TCP PUSH indicator, theappliance may send all buffered data corresponding to the TCP connectionfor encryption and transmission.

In still another embodiment, a transmittal condition may comprise theexpiration of a timer corresponding to one or more buffered messages.For example, an appliance may be configured to encrypt and transmit allbuffered data within a maximum of 20 ms after buffering the data. Uponexpiration of the timer corresponding to a given buffered message, theappliance may send the buffered data for encryption and transmissionAfter determining that a transmittal condition has been satisfied (step711); the appliance may, in response to the determination, encrypt thefirst decrypted message and a portion of the second decrypted message toproduce a third SSL record (step 713). In some embodiments, thisencryption may be done by a cryptographic processing card. In someembodiments, the appliance may encrypt the messages using the samealgorithm used to decrypt the messages. In other embodiments, theappliance may encrypt the messages using a different algorithm than thealgorithm used to decrypt the messages. In some embodiments, the thirdSSL record may comprise the same SSL protocol as the first and secondrecords. In other embodiments, the third SSL record may comprise adifferent SSL protocol than the first and second SSL records.

After producing a third SSL record (step 713); the appliance maytransmit, via a second connection, the third record (step 715). Thistransmission may be addressed to any computing device including aclient, server, or second device. The second connection may comprise anyprotocol or protocols described herein.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A method for buffering SSL handshake messages prior to computing amessage digest for the SSL handshake, the method comprising: (a)conducting, by an appliance with a client, an SSL handshake, the SSLhandshake comprising a plurality of SSL handshake messages; (b) storing,by the appliance, the plurality of SSL handshake messages; (c)providing, by the appliance to a message digest computing device inresponse to receiving a client finish message corresponding to the SSLhandshake, the plurality of SSL handshake messages; (d) receiving, bythe appliance from the message digest computing device, a message digestcorresponding to the provided messages; (e) determining by theappliance, the message digest matches a message digest included in theSSL client finish message; and (f) completing, by the appliance with theclient, the SSL handshake.
 2. The method of claim 1, wherein step (a)comprises conducting, with a client by an appliance providing access toat least one server, an SSL handshake, the SSL handshake comprising aplurality of SSL handshake messages.
 3. The method of claim 1, whereinstep (a) comprises conducting, by an appliance with a client, an SSLhandshake, the SSL handshake comprising a plurality of SSL handshakemessages, the plurality of SSL handshake messages comprising theentirety of messages received and transmitted in conducting the SSLhandshake.
 4. The method of claim 1, wherein step (a) comprisesconducting, by an appliance with a client, an SSL handshake, the SSLhandshake comprising a plurality of SSL handshake messages, theplurality of SSL handshake messages comprising a client hello message, aserver hello message, and a client key exchange message.
 5. The methodof claim 1, wherein step (c) comprises providing, by the appliance to adedicated cryptographic processing card in response to receiving aclient finish message corresponding to the SSL handshake, the pluralityof SSL handshake messages.
 6. The method of claim 1, wherein step (b)comprises storing, by the appliance, the plurality of SSL handshakemessages, each message having an associated length and each messagestored in a buffer location.
 7. The method of claim 6, wherein step (c)comprises providing, by the appliance to a message digest computer inresponse to receiving a client finish message corresponding to the SSLhandshake, the associated lengths and locations of the plurality of SSLhandshake messages.
 8. The method of claim 6, wherein step (c) comprisesproviding, by the appliance to a dedicated cryptographic processing cardin response to receiving a client finish message corresponding to theSSL handshake, the associated lengths and locations of the plurality ofSSL handshake messages.
 9. The method of claim 1, wherein step (f)comprises transmitting, by the server to the client, an SSL serverfinish message.
 10. A computer implemented system for buffering SSLhandshake messages prior to computing a message digest for the SSLhandshake, the system comprising: a network appliance which conducts,with a client, an SSL handshake, the SSL handshake comprising aplurality of SSL handshake messages; storing, by the appliance, theplurality of SSL handshake messages; providing, to a message digestcomputing device in response to receiving a client finish messagecorresponding to the SSL handshake, the plurality of SSL handshakemessages; receiving, from the message digest computing device, a messagedigest corresponding to the provided messages; determining, the messagedigest matches a message digest included in the SSL client finishmessage; and completing, with the client, the SSL handshake; and amessage digest computing device which computes a message digestcorresponding to one or more received messages.
 11. The system of claim10, wherein the appliance provides access to at least one server. 12.The system of claim 10, wherein the appliance conducts, with a client,an SSL handshake, the SSL handshake comprising a plurality of SSLhandshake messages, the plurality of SSL handshake messages comprisingthe entirety of messages received and transmitted in conducting the SSLhandshake.
 13. The system of claim 10, wherein the appliance conducts,with a client, an SSL handshake, the SSL handshake comprising aplurality of SSL handshake messages, the plurality of SSL handshakemessages comprising a client hello message, a server hello message, anda client key exchange message
 14. The system of claim 10, wherein theappliance provides, to a dedicated cryptographic processing card inresponse to receiving a client finish message corresponding to the SSLhandshake, the plurality of SSL handshake messages.
 15. The system ofclaim 10, wherein the appliance stores the plurality of SSL handshakemessages, each message having an associated length and each messagestored in a buffer location.
 16. The system of claim 15, wherein theappliance provides, to a message digest computer in response toreceiving a client finish message corresponding to the SSL handshake,the associated lengths and locations of the plurality of SSL handshakemessages.
 17. The system of claim 15, wherein the appliance provides, toa dedicated cryptographic processing card in response to receiving aclient finish message corresponding to the SSL handshake, the associatedlengths and locations of the plurality of SSL handshake messages. 18.The system of claim 10, wherein the appliance transmits, to the client,an SSL server finish message.